Bassanite
A variety of Minerals
What is Bassanite?
Bassanite is a calcium sulfate mineral with formula CaSO4·1/2H2O or 2CaSO4·H2O. In other words it has half a water per CaSO4 unit hence its synonym calcium sulfate hemihydrate. Bassanite was first described in 1910 for an occurrence on Mount Vesuvius. It was named for Italian paleontologist Francesco Bassani (1853–1916). At Vesuvius it occurs as alterations from gypsum within leucite tephrite and as fumarole deposits. It occurs in dry lake beds in California and Australia. It also occurs interlayered with gypsum in caves. H. Schmidt and coinvestigators reported in 2011 that under dry conditions, the structure is monoclinic with space group C2, but at 75% humidity, the structure is trigonal with space group P3221. This reflects the incorporation of additional water of hydration, such that the trigonal form has the formula CaSO4·0.625H2O
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Bassanite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Bassanite Localities Map
See where Bassanite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Quick Facts
Physical Properties
- Color
- White
- Density
- 2.69 - 2.76 g/cm³
Chemical Properties
- Chemical Formula
- Ca(SO4) · 0.5H2O
- Elements
- Ca, H, O, S
Also Known As
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Bassanite FAQs
How do I identify Bassanite?
Bassanite can be identified by its White color. Look for these key characteristics when examining specimens.
What color is Bassanite?
Bassanite typically appears in White. Color can vary depending on impurities and formation conditions.
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